HDFS-4818. Merging change r1494023 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1494024 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1494027 from trunk to branch-2 to fix YARN-840. Moved ProtoUtils to yarn.api.records.pb.impl. Contributed by Jian He.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1494029 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-MAPREDUCE-4884-branch-2-gd